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174

Milling' Machine.

Figs. 175 and 178, which is connected by a shaft with the din
At every rotation of the cam a vibration is given to the lev*
which is connected to the lever u (Fig. 179), carrying a rat
pawl, and a partial rotation of shaft v (Fig. 175) thus obtai
Both levers are provided with slots to adjust the amount of fe

The table w to support the work, is circular in form, and
worm teeth on its lower rim.    It is mounted on two slides x
Y, which are again supported on the bed slide z.    The sha
turns the bed screw g through the wheels e and f, giving a lo
tudinal feed, useful for cotter holes and such like.    Putting/
of gear by sliding, a cross feed is effected by wheels a and d,
former taking its motion from v by mitre gear, and the la
being fixed  on the cross  slide screw h,  so  that Y would
stationary and x would traverse.    The third feed is a rotatiot
the table obtained by the worm gearing above mentioned;
wheel d being slid out of gear, and b put in, the worm shaft ^
rotated, and its motion transmitted to wheel k, cast on the tal
This motion is analogous to that of the shaping machine mand

It has been customary to attach the tool directly to the n
and let the point scrape on the work during its return, giv
useless friction and wear, but it is now recognised that a flap
advisable, and such a tool box has been shewn. A spring on i
front or counter-balance at the back is necessary to bring the t
back to its work, gravity not being otherwise employable.

The form of tool may be as for previous machines.

The   Milling  Machine, though in  its  present  form
recent introduction, has been known for a very long period; \
it was not till milling cutters or ' mills' were produced  m<
cheaply and correctly by emery grinders that the principle coij
be sufficiently extended.                                                         1

Cutter.—As already mentioned, a rotating cutter is employs
to which the work is fed, and this we shall first discuss. Fig. ij
represents a spiral mill for tooling flat surfaces. All these mi
are keyed to a mandrel or cutter spindle, which is either rotati
between centres, or fixed into the catch plate and only centred!
its opposite end. Fig. 182 shews a key-seating or groovii
cutter for cutting key ways or as a parting tool Being giwuj
both on circumference and sides, it becomes narrower at ea^
re-grinding, and therefore inaccurate. This can be avoided \